Huawei: Fix create volume with prefetch value error
Huawei: Fix create volume with prefetch value error

In Huawei driver, when we create volume with
prefetch configurated in xml, the prefetch value
on the array is incorrect. So fix it.

Change-Id: I69b81eec47ae7663857cfb461aba32109746dbc0
Closes-Bug: #1549161

j-griffith/cinder,Nexenta/cinder,NetApp/cinder,Datera/cinder,eharney/cinder,cloudbase/cinder,ge0rgi/cinder,bswartz/cinder,Hybrid-Cloud/cinder,openstack/cinder,bswartz/cinder,cloudbase/cinder,j-griffith/cinder,eharney/cinder,openstack/cinder,Nexenta/cinder,Datera/cinder,mahak/cinder,NetApp/cinder,phenoxim/cinder,phenoxim/cinder,Hybrid-Cloud/cinder,mahak/cinder